Search or add a thesis

Advanced Search (Beta)
Home > Development and Electrochemical Characterization of Nanocomposites for Biogas Based Fuel Cells

Development and Electrochemical Characterization of Nanocomposites for Biogas Based Fuel Cells

Thesis Info

Access Option

External Link

Author

Rafique, Asia

Program

PhD

Institute

COMSATS University Islamabad

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2019

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/10572/1/Asia_Rafique_Physics_2019_CIIT_10.07.2019.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676725855336

Similar


Development and Electrochemical Characterization of Nanocomposites for Biogas Based Fuel Cells There is an urgent need to explore affordable and renewable energy resources because of the decline in reserves of fossil fuels. Biomass is an abundantly available resource in nature and can be used to generate energy in a sustainable manner. Fuel cells deliver a combination of advantages and make use of renewable energy sources. Solid oxide fuel cells (SOFCs), specifically, overcome the petroleum scarcity issue by using biofuel. The aim of this thesis is the development of nanocomposite electrolytes and anode composite catalysts for low-temperature SOFCs fuelled with biogas for clean energy applications. In the present work, Sr/Sm-doped ceria (Sr-SDC) nanocomposite electrolytes with a core shell structure are synthesized with different compositions for low temperature SOFCs. A co-doping technique is successfully used to achieve a significant enhancement in the ionic conductivity of 0.50 S/cm at 600 ˚C for the nanocomposite electrolyte Sr0.1Sm0.1Ce0.8O2-δ-carbonate. The carbonate phase (shell layer) acts as a barrier and protects the SDC (core) from the partial reduction by the fuel. This carbonate shell introduces an interface between these two phases, which is the key to realizing the interfacial super-ionic conduction pathways. This work also describes the development of ceria electrolytes that are doped and co-doped with lanthanum (La) and zirconium (Zr) and show excellent thermal stability. The ionic conductivity of La0.2Ce0.8O2-δ (LDC), Zr0.2Ce0.8O2-δ (ZDC) and Zr0.2La0.2Ce0.6O2-δ (ZLDC) has been measured in the temperature ranges of 450 °C to 650 °C and LDC achieved a high ionic conductivity of 0.81 × 10-2 S/cm. Thermal expansion coefficients (TECs) of these electrolytes have also been found to have good concurrence and compatibility with commonly used electrolytes and electrodes. The main objective of this work is the development of stable and active anode catalysts that run over biogas as well as hydrogen for low temperature SOFCs. The anode composite Ni0.6Zn0.4Gd0.2Ce0.8O2-δ (NiZn-GDC) has been developed that exhibits semiconductor conductive behaviour, and a maximum conductivity of 1.37 S/cm has been achieved at 600 ˚C. This composite anode is found to have excellent thermally stability as well as being carbon resistant to coking during testing with biogas. A maximum power density of 820 and 548 mW/cm2 has been reported with hydrogen and biogas fuels, respectively, at 600 ˚C. This thesis also describes Ni-based and Ni-free anode catalysts NiLiCu-oxide with LDC for SOFCs fuelled with biogas. The anode composite NLC622-LDC has reported a maximum DC conductivity of 3.47 S/cm with Pmax of 650 and 390 mW/cm2 for hydrogen and biogas, respectively, at 600 ˚C. A Ni free anode catalyst Zn0.2Li0.2Cu0.6O2-δ (ZnLiCu-oxide) is also developed as a potential candidate for biogas-based SOFCs that bypasses the difficulty of carbon deposition and has a maximum conductivity of 4.0 S/cm at 600 ˚C. An open circuit voltage (OCV) of 0.96 V is achieved with maximum power density of 600 mW/cm2 with biogas (50% methane) at 650 ˚C. In the present work, a theoretical model of FC system has been designed using MATLAB software, and it makes use of biomass (animal waste, redwood, rice husk and sugar cane). In the last part of the thesis, a partial research work has been conducted to cast the tapes of NiO-GDC (NiO-Gd0.1Ce0.9O1.95) as anode and GDC (Gd0.1Ce0.9O1.95) as electrolyte via aqueous tape casting method. The aqueous tape casting is an emerging and cost-effective technique for the commercialization of SOFCs but faces challenges with ceria tapes due to its poor mechanical strength and co-sintering of half-cells.
Loading...
Loading...

Similar Books

Loading...

Similar Chapters

Loading...

Similar News

Loading...

Similar Articles

Loading...

Similar Article Headings

Loading...

غزل

ہفت افلاک کا عنوان ہوا کرتا تھا : جب ستارہ مر ا ذیشان ہوا کرتا تھا

چین اس کو بھی گھڑی بھر کو میسر نہیں تھا : اُن دنوں میں بھی پریشان ہوا کرتا تھا

اُن دنوں دھول تھی اتنی نہ دھؤاں پھیلا تھا : دیکھ لینا تجھے آسان ہوا کرتا تھا

خال و خد حسن کا معیار بڑھا دیتے ہیں : میں اُسے دیکھ کے حیران ہوا کرتا تھا

پھر کسی نے دلِ ویران کا در باز کیا : یہ علاقہ تو بیابان ہوا کرتا تھا

ہے کوئی اُس سا حسیں شخص تو آگے آئے

پورے کیمپس میں یہ اعلان ہوا کرتا تھا

٭

آج محفل میں اسے دیکھ کے یاد آئی بہت

داستاں چاند کی جو ہم نے سنی نانی سے

اس ستم گر سے مجھے زخم ملیں گے جتنے

وہ منالے گا مجھے اتنی ہی آسانی سے

جب سے آئے ہیں خریدار چراغوں کے  نوید

تیرگی بڑھنے لگی شہر  میں تابانی سے

 

When Comes such Another? Asma Jahangir 1952 –2018

On the 11th of February this year death vanquished Pakistan’s Asma Jahangir: Nothing else could. Her name will endure; yet one cannot go on to say “death thou art dead” for the vacuum in the field where this indomitable and intellectually gifted lawyer fought and won her battles for the forgotten and ignored, the resource-less, and – above all – for the politically and socially persecuted is felt more gravely with each passing day: Asma Jahangir was a convinced human rights activist. There are many such, but she was a uniquely effective and successful one.

Identification of Temporal Specificity and Focus Time Estimation in News Documents

Time is deemed as paramount aspect in Information Retrieval (IR) and it pro foundly influence the interpretation as well as the users intention and expectation. The temporal patterns in a document or collection of documents plays a central role in the effectiveness of IR systems. The accurate discernment plays an immense role in persuading the time-based intention of a user. There exists a plethora of documents on the web wherein most on them contain the divergent temporal pat terns. Assimilation of these temporal patterns in IR is referred to as Temporal Information Retrieval (TIR). The comprehension of TIR systems is requisite to address the temporal intention of a user in an efficient manner. For time specific queries (i.e. query for an event), the relevant document must relate to the time period of the event. To attenuate the problem, the IR systems must: determine whether the document is temporal specific (i.e. focusing on single time period) and determine the focus time (to which the document content refers) of the documents. This thesis exploits the temporal features of the news documents to improve the retrieval effectiveness of IR systems.As best to our knowledge, this thesis is the pioneer study that focuses on the problem of temporal specificity in news docu ments. This thesis defines and evaluate novel approaches to determine the tem poral specificity in news documents. Thereafter, these approaches are utilized to classify news documents into three novel temporal classes. Furthermore, the study also considers 24 implicit temporal features of news documents to classify in to; a) High Temporal Specificity (HTS), b) Medium Temporal Specificity (MTS), and c) Low Temporal Specificity (LTS) classes. For such classification, Rule-based and Temporal Specificity Score (TSS) based classification approaches are proposed. In the former approach, news documents are classified using a proposed set of rules that are based on temporal features. The later approach classifies news documents based on a TSS score using the temporal features. The results of the proposed approaches are compared with four Machine Learning classification algorithms: Bayes Net, Support Vector Machine (SVM),Random Forest and Decision Tree. x The outcomes of the study indicate that the proposed rule-based classifier outper forms the four algorithms by achieving 82% accuracy, whereas TSS classification achieves 77% accuracy. In addition, to determine the focus time of news documents, the thesis contem plates the temporal nature of news documents. The type and structure of doc uments influence the performance of focus time detection methods. This thesis propose different splitting methods to split the news document into three logical sections by scrutinizing the inverted pyramid news paradigm. These methods in clude: the Paragraph based Method (PBM), the Words Based Method (WBM), the Sentence Based Method (SBM), and the Semantic Based Method (SeBM). Temporal expressions in each section are assigned weights using a linear regres sion model. Finally, a scoring function is used to calculate the temporal score for each time expression appearing in the document. Afterwards, these temporal expressions are ranked on the basis of their temporal score, where the most suit able expression appears on top. Two evaluation measures are used to evaluate the performance of proposed framework, a) precision score (P@1, P@2) and average error years. Precision score at position 1 (P@1) and position 2 (P@2) represent the correct estimation of focus at the top 2 positions in the ranked list of focus time whereas, average error year is the distance between the estimated year and the actual focus year of news document. The effectiveness of proposed method is evaluated on a diverse dataset of news related to popular events; the results re vealed that the proposed splitting methods achieved an average error of less than 5.6 years, whereas the SeBM achieved a high precision score of 0.35 and 0.77 at positions 1 and 2 respectively. The overall findings presented in this thesis demonstrate that the valuable tempo ral insights of documents can be used to enhance the performance of IR systems. The time aware information retrieval systems can adopt these findings to satisfy the user expectation for temporal queries.